Field of the Invention
The invention relates to a control apparatus using variations in conduction angle as control command, particularly to a control apparatus applicable to DC (Direct Current) inverter motor, lamp, heater or other appliance apparatus.
Brief Description of the Related Art
A traditional leading edge cutoff phase control dimmer (known as TRIAC dimmer) controls energy transferred to load by adjusting conduction angle of alternating current. However, minimum conduction angle usually has to approximate to zero degree for deep dimming, such that power factor is reduced and electronic load operates abnormally.
Referring to FIG. 1A, which is a circuit structure diagram showing a conventional TRIAC dimmer. As shown in the figure, basic elements of the circuit include an AC (Alternating Current) power supply AC, a variable resistance R1, a fixed resistance R2, a capacitor C1, a diode thyristor DIAC, a triode thyristor TRIAC and a load LOAD. Wherein, the RC circuit consisting of the variable resistance R1, the fixed resistance R2 and the capacitor C1 may postpone activation of the TRIAC dimmer until the voltage of the capacitor C1 rises to the trigger voltage of the diode thyristor DIAC.
In other words, after electric supply is connected, current will flow through the variable resistance R1 and the fixed resistance R2, followed by flowing into and charging the capacitor C1. After the voltage of the capacitor C1 reaches the trigger voltage of the diode thyristor DIAC, the diode thyristor DIAC is conducted, and then, the triode thyristor TRIAC is triggered for conduction and starts to supply power to light source. In the following, the variable resistance R1, the fixed resistance R2, and the connection of the variable resistance R1 and the fixed resistance R2 are referred to as “conduction angle modulation module” collectively.
Furthermore, refer to both FIG. 1B and FIG. 1C. FIG. 1B shows a full sinusoidal voltage waveform on input end. FIG. 1C shows a voltage waveform on two ends of the light source after being chopped by the TRIAC dimmer. Wherein, as the variable resistance R1 is modulated such that a slider slides downwards further, the resistance of the variable resistance R1 becomes larger, the current flowing through the capacitor C1 is reduced, the voltage across the capacitor C1 will reach the trigger voltage of the diode thyristor DIAC slower, and the triode thyristor TRIAC will be triggered slower for conduction, such that the chopped portion of the input sine wave voltage results in reduced energy supplied to the light source (luminance is reduced), as shown in FIG. 1C. In brief, larger resistance of the variable resistance R1 results in smaller conduction angle θ, smaller electricity supplied to the light source, and less luminance, so that the power factor is getting lower and lower.
Further, for the structure and function of the traditional leading edge cutoff phase control dimmer (also referred to as small conduction angle dimmer) as described above, the conduction angle of the dimmer may be changed by sizing the variable resistance R1, or sum of the variable resistance R1 and the fixed resistance R2, such that the delay time for activating the TRIAC dimmer may be adjusted. Wherein, the main function of the fixed resistance R2 is to keep a basic resistance as the variable resistance R1 is adjusted to 0 ohm in order to prevent excessive current, which can damage the capacitor C1, from flowing to the capacitor C1. Certainly, the resistance of the fixed resistance R2 may also influence the conduction angle of the dimmer. However, as the variable resistance R1 is adjusted to the maximum value, the delay time for activating the TRIAC dimmer is the longest, and the conduction angle is the minimum and is close to 0, so that such dimmer is referred to as small conduction angle dimmer, which results in lower power factor and abnormal operation of electronic load in deep dimming.
However, for lower power factor of conventional technology due to small conduction angle, the applicant has proposed improved solutions of new concepts and has applied for patents thereof, such as PCT application No. PCT/CN2013/086093, titled “Method for Controlling and Operating Load by Using Control Command of Changing Conduction Angle of AC Voltage and Adjustment and Control Apparatus thereof”, and PCT application No. PCT/CN2013/086087, titled “Control Apparatus for DC Variable Frequency Motor”, which use conduction angle as control command essentially, rather than simple control for transfer of excessive energy. Thereby, the minimum conduction angle may be controlled to be larger than 120 degrees in normal operation (referred to as large conduction angle dimmer), so that the issue of lower power factor when traditional TRIAC dimmer is used described above may be overcome, electronic load may be protected from abnormal operation due to excessively small conduction angle, and control of multiple functions is available by using different phase commands.
Additionally, there are many commercially available traditional dimmer products. That is, light bulbs or motors are driven by using traditional dimmers. However, in the case that traditional dimmers may be modified to new dimmers of large conduction angle, or large conduction angle dimmers may be switched to traditional small conduction angle dimmers when loads of traditional dimmers are used, the products may become more convenient and more popular, and are of urgent needs in industries.